Shim change question...

[RCS]

This Saturday I plan to change the shim in my front exhaust valve on the #2 cylinder. This is the only shim change needed based on my valve clearance check a few weeks ago.

My bike has 16,000 miles on it. The current clearance is .18mm. The ideal clearance is .25mm +/- .03mm. I received the Hot Cams shims today and have a choice of changing the shim in .05mm increments.

So, I can either change the clearance to .23mm or .28mm. Which shim change would you make on this exhaust valve?

 

[ChucksKLRST]

This Saturday I plan to change the shim in my front exhaust valve on the #2 cylinder. This is the only shim change needed based on my valve clearance check a few weeks ago.

My bike has 16,000 miles on it. The current clearance is .18mm. The ideal clearance is .25mm +/- .03mm. I received the Hot Cams shims today and have a choice of changing the shim in .05mm increments.

So, I can either change the clearance to .23mm or .28mm. Which shim change would you make on this exhaust valve?

I would change it to the loose side as exhaust valves tend to tighten up.
.28

 

[RCS]

Once I take out the cam on Saturday, would it be worth taking a run down to the local Honda dealer to see if they have the perfect shim or would that be a waste of time?

 

[ChucksKLRST]

Once I take out the cam on Saturday, would it be worth taking a run down to the local Honda dealer to see if they have the perfect shim or would that be a waste of time?

Call them before you go. They migh not have it in STock. Also Suzuki uses the same shims as Honda. I was able to get a couple of shims from the Suzuki dealer once. As long as you are in tolerance all is good.

 

[Byron]

BMW's also use the same size shims from what I'm told. I'd measure the Hot Cams shim as they may vary slighlt from what they are marked. If they have a shim that puts you in spec, loose side better, then just do it. it isn't going to make that much of a difference.

 

[Blrfl]

Measure every shim before installing it, no matter how good you think the source is.

--Mark

 

[Scooter]

Once I take out the cam on Saturday, would it be worth taking a run down to the local Honda dealer to see if they have the perfect shim or would that be a waste of time?

Waste of time. As long as you wind up within the tolerance range you're good to go. You would be better off recording all of the shim sizes from the other seven shims as long as you have access to them. That way, if any of them go out of spec in the future you can calculate your ideal size shim before taking everything apart again.

I'd go with the looser spec than the tighter one.

 

[RCS]

Measure every shim before installing it, no matter how good you think the source is.

--Mark

Yes, I plan on doing this. I also purchased and now have in hand an inexpensive ($10) Micrometer that is calibrated to .01mm. Is that sufficient or should I opt for a more exact Micrometer that measures to the .001 for $50 - (good deal and maybe I'm just itching for a reason to pull the trigger on another new tool purchase)?

 

[Blrfl]

At these sizes, an inexpensive micrometer is more than sufficient. (Although as micrometers go, $50 is inexpensive.)

But on the other hand, you should never resist the urge to buy more tools...

--Mark

 

[John OoSTerhuis]

The Honda shims are in .025mm increments. You might want to try those instead when doing your calculations.

 

[RCS]

The Honda shims are in .025mm increments. You might want to try those instead when doing your calculations.

The way I figure it my current clearance is .18mm and it should be .25mm.

My options are: (a) go with a Hot Shims shim that ranges in .05mm increments so I can change the clearance to either .23mm or .28mm - both of these are in specifications, or (b) hope the local Honda store has the right shim to get me to .255mm clearance since the Honda shims go in .025 increments.

Given the time required to change the shim I would ideally like to make the perfect change. However, I'll probably go with the Hot Shims shim and larger clearance since I don't want to leave the cam shaft off the bike while I "run to the store". Plus, after doing the valve clearance check I found it would be difficult for me to accurately measure a gap difference of less than .01mm.

 

[John OoSTerhuis]

Bob, you might find the info in these threads of interest:

https://www.st-owners.com/forums/showthread.php?t=76700
https://www.st-owners.com/forums/showthread.php?t=34494

Every Honda shim that I've ever mic'd with my micrometer was right on spec/what it was marked as (see the list in the first thread).

Measure in thousandths of an inch and forget the metric... JMHO

HTH

Regards, John

 

[RCS]

Bob, you might find the info in these threads of interest:

https://www.st-owners.com/forums/showthread.php?t=76700
https://www.st-owners.com/forums/showthread.php?t=34494

Every Honda shim that I've ever mic'd with my micrometer was right on spec/what it was marked as (see the list in the first thread).

Measure in thousandths of an inch and forget the metric... JMHO

HTH

Regards, John

Thanks for the thread links. I believe I have read each and every thread in this section of the site as well as both of Curt's discussions on the subject of valve clearance and shim changes. I wouldn't have even thought about doing this job without the website and all its great contributors!

Regarding inches versus metric. I'm a fan of "when in Rome do as the Romans do". Since the Honda is a Japanese bike I'm going to stick with the metrics. I find metrics easy to work with.

 

[George]

I just did ReSTored last week. After my initial screw up I used John's suggestion, 1/1000in = .025mm. I used Mark's kit plus the shims from The Hulk and brought all valves (14 of 16 as close as possible to center, loose side if necessary. Rode her for the AZ RTE yesterday and another 120 miles today, all is good. There were/are several Honda shims in the kit (benefit of shipping it around the country) so I was able to get close to nominal on every valve. Several of mine went from #202 to #198 (effectively 2 sizes, from one size too tight to nominal.)

BTW, I stripped the bottom/rear bolt on the right side (one of the long ones.) Only 9 ft/lbs of torque, easy to strip in my estimate. Found a slightly longer bolt at NAPA that still fit the hole and was able to torque it okay. Not gonna worry about it.

STick is next, she hasn't had a shim change in 135,000 miles. One exhaust is .002" too tight (.003 from nominal). I'll fix that and any others that our of nominal on that cam. All else is good.

By the way, that one valve has been .001 too tight for a loooooooooooong time. Just changed in the last 10,000 miles (since last check.)

 

[Silver Bullet]

++ on John O,s thinking in Thousands of an inch over mm,s. As a long time machinist and working With close tolerances every day ,it,s go with what you know I guess. If it,s mm.s just take and divide by 25.4 to convert to inches . example .25mm\25.4=.0098 0f an inch. Oh well just throwing out thoughts!

MIKE

 

[John OoSTerhuis]

.... Regarding inches versus metric. I'm a fan of "when in Rome do as the Romans do". Since the Honda is a Japanese bike I'm going to stick with the metrics. I find metrics easy to work with.

Not to beat a dead horse here (see my posts in the threads links above), but...

-- one thousandth of an inch equals .0254mm and the smallest clearance change you can make is the Honda shim size increment of .025mm --

When in Rome...? Here's what your shop tech will do: measure in thousandths of an inch, pull the shim bucket and then the shim under it, read the marking on the shim, look at the shim list and then pick the correctly marked replacement shim out of his box (one size/increment thinner or thicker than the current shim for every thousandth of an inch of desired change), install it and button up the ST. No math involved.

Unless you custom grind a shim to the exact thickness that the most accurately possible metric measurement and the formula calls for... you're stuck with .025mm as the smallest valve clearance change you can make. And .025mm equals .00098452 inches... virtually .001 inch and close enough for our purposes.

Simple is good... and foolproof as long as you remember:
- to increase clearance use a thinner shim
- to decrease clearance use a thicker shim
- one Honda shim size per thousandth of inch of desired change

Just saying...

 

[George]

Certainly can't argue with John's logic. Most problems come from trying to convert Metric <--> Inch and vice-versa. If ya go with the simple solution, the numbers don't really count expect as markers, go bigger or smaller as needed.

As I understand it, a good tech does go - no go measurements, that is (example is for exhaust valve on an 1100.

Loose is .011, tight is .009. Check with the 11, go is loose, check with the 9, no go is tight. If the 11 doesn't fit (or just does fit) and the 9 does fit, it's perfect. No need to even check with a .010.

I'm just about to start on STick, I'll let y'all know the results.

 

[RCS]

I understand the issue. Everything on the Honda is metric. All my motorcycle tools are metric including the feeler gauges, micrometer, shims, socket set, etc. So I don't feel the need to make any inch conversions for working on the Honda.

Whatever shim is under that shim bucket to give me the .18mm clearance I can only move in either .025mm or .05mm increments. So, using a smaller shim I can go to .255mm clearance (3x.025mm+.18mm) using the Honda shim or to a .28mm clearance (2x.05mm+.18mm) with the Hot Shim shim.

Its all good! Thanks to everyone for all the terrific information that has given me the confidence to take off the cam and change a shim!